Signal transmission through LC resonant circuits

ABSTRACT

An embodiment of an electronic system includes a first electronic circuit and a second electronic circuit. The electronic system further includes a resonant LC circuit having a resonance frequency for coupling the first electronic circuit and the second electronic circuit; each electronic circuit includes functional means for providing a signal at the resonance frequency to be transmitted to the other electronic circuit through the LC circuit and/or for receiving the signal from the other electronic circuit. The LC circuit also include capacitor means having at least one first capacitor plate included in the first electronic circuit and at least one second capacitor plate included in the second electronic circuit. The LC circuit further includes first inductor means included in the first electronic circuit and/or second inductor means included in the second electronic circuit. The at least one capacitor plate of each electronic circuit is coupled with the corresponding functional means through the possible corresponding inductor means.

PRIORITY CLAIM

The instant application claims priority to Italian Patent ApplicationNo. MI2009A001825, filed Oct. 21, 2009, which application isincorporated herein by reference in its entirety.

RELATED APPLICATION DATA

This application is related to U.S. patent application Ser. No.12/907,839, entitled “TESTING OF ELECTRONIC DEVICES THROUGH CAPACITIVEINTERFACE”, filed Oct. 19, 2010, and which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

One or more embodiments generally relate to the field of electronics.More specifically, such embodiments relate to the field of wirelesstransmission of signals and/or power among electronic circuits.

BACKGROUND

An electronic system may be formed by a plurality of electroniccircuits, each one being capable of performing a specific function ofthe system. Among the design issues that are encountered in thedevelopment of an electronic system, one of particular relevance isgiven by the coupling among the electronic circuits thereof.

In a solution being known in the state of the art and commonly used fora large number of electronic systems available in the market, thecoupling among the electronic circuits is performed through electricalconnections. For example, such electrical connections may be implementedby interconnection metal tracks being arranged on an insulating supportthat is shared among the electronic circuits.

However, such interconnection tracks are subject to parasitic effects(for example, resistive, inductive and capacitive ones) that limit themaximum frequency of the signals (thereby affecting the speed ofcommunication and execution of the operations) and that may implyunwanted power dissipation.

A known solution of the above-mentioned drawbacks provides for thecoupling among the electronic circuits through electromagnetic waves. Inorder to transmit and/or receive the desired signals, the electroniccircuits are provided with antennas. There exist solutions in which theantennas are of capacitive type; such capacitive antennas are devicesthat mainly use the electric field and, by means of electric induction,translate a voltage variation into an electromagnetic disturbance, andvice-versa, depending on whether they are used for transmission orreception. However, the capacitive antennas may be capable of onlytransmitting and receiving signals, but not a power supply. There alsoexist opposite solutions in which the antennas are of inductive type andthey are included, for example, in parallel resonant LC circuits (thatis, formed by an inductor and a capacitor being connected in parallel).Such inductive antennas mainly use the magnetic field and they aredevices that, by means of magnetic induction, translate a currentvariation into an electromagnetic disturbance, and vice-versa, dependingon whether they are used for transmission or reception.

However, such solutions may have some drawbacks that make them notalways conveniently applicable in any electronic system. Particularly,the use of resonant LC circuits (for example, of parallel type) beingembedded in the electronic circuits may occupy an excessive area, andthis is often incompatible with the needs of reduced size.

Such drawback may be solved by implementing each inductive antenna in anupper area of the electronic circuit (without any increase in the areaoccupation of the electronic circuit). However, both in the case thatthe antenna is formed within the electronic circuit and in the case thatthe antenna is formed above it, the implementation of the coupling beingbased on inductive antennas substantially requires that each electroniccircuit being part of the electronic system should be provided with atleast one resonant LC circuit. This implies an increase in the number ofrequired components and in the production costs.

SUMMARY

In its general terms, an embodiment is based on the idea of distributingthe resonant LC circuits across different circuits.

More specifically, an embodiment is an electronic system including afirst electronic circuit and a second electronic circuit. The electronicsystem further includes a resonant LC circuit having a resonancefrequency for coupling the first electronic circuit and the secondelectronic circuit; each electronic circuit includes functional meansfor providing a signal at the resonance frequency to be transmitted tothe other electronic circuit through the LC circuit and/or for receivingthe signal from the other electronic circuit. An embodiment, the LCcircuit includes capacitor means having at least one first capacitorplate included in the first electronic circuit and at least one secondcapacitor plate included in the second electronic circuit. The LCcircuit further includes first inductor means included in the firstelectronic circuit and/or second inductor means included in the secondelectronic circuit. The at least one capacitor plate of each electroniccircuit is coupled with the corresponding functional means through thepossible corresponding inductor means.

Another embodiment is a corresponding transmission method.

The same features being recited in the dependent claims for theelectronic system may apply mutatis mutandis to the method.

A further embodiment is an electronic circuit for use in such electronicsystem.

A different embodiment is a complex apparatus including one or more ofsuch electronic systems.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments, as well as further features and the advantagesthereof, may be best understood with reference to the following detaileddescription, given purely by way of a non-restrictive indication, to beread in conjunction with the accompanying drawings (whereincorresponding elements are denoted with equal to similar references, andtheir explanation is not repeated for the sake of exposition brevity).In this respect, it is expressly intended that the figures are notnecessarily drawn to scale and that, unless otherwise indicated, theyare simply used to conceptually illustrate the described structures andprocedures. In particular:

FIG. 1A schematically shows an electronic system according to anembodiment,

FIG. 1B schematically shows an electronic system according to anotherembodiment,

FIG. 2A-2E schematically show different implementations of an electroniccircuit according to corresponding embodiments,

FIG. 2F schematically shows two electronic circuits in cross-sectionaccording to another embodiment,

FIG. 3A schematically shows different implementations of an electroniccircuit in top view according to corresponding embodiments,

FIG. 3B schematically shows an implementation of an electronic circuitin cross-section according to another embodiment,

FIG. 4A schematically shows an electronic system according to anotherembodiment,

FIG. 4B schematically shows an electronic system according to a furtherembodiment,

FIG. 5A schematically shows an implementation of the electronic systemof FIG. 4A according to an embodiment, and

FIG. 5B schematically shows an implementation of the electronic systemof FIG. 4A according to another embodiment.

DETAILED DESCRIPTION

In particular, in FIG. 1A there is schematically shown an electronicsystem 100 a exploiting wireless signal transmission according to anembodiment.

The electronic system 100 a may include a plurality of electroniccircuits; for the sake of description simplicity, there are considered,by way of example in no way limitative, a first electronic circuit 105 aand a second electronic circuit 105 a′ of the electronic system 100 a.

Each electronic circuit 105 a, 105 a′ includes a correspondingfunctional region 108 a, 108 a′; the functional region 108 a, 108 a′ isformed by circuit elements (not shown in the figure) implementingspecific functions of the electronic circuit 105 a, 105 a′ and by atransmission and/or reception block (for example, a transceiver, oralternatively a transponder) 110 a, 110 a′ for managing signaltransmissions and/or reception between the electronic circuits 105 a and105 a′, and vice-versa.

Such signals may be operative signals, which are used for transmitting acorresponding information content (for example, being properly encodedand modulated onto a carrier wave by any known communication technique).

In addition or in alternative, such signals may be supply signals, whichconsist of an alternate carrier wave that may be used for transmittingenergy capable of supplying another system—for example, being used inreception for creating a direct voltage through an AC/DC converterperforming an operation of rectification, filtering, and possibleregulation.

Each transceiver 110 a, 110 a′ is provided with input/output terminals103 a, 103 a′ for receiving and/or transmitting such signals, and with areference terminal 104 a, 104 a′ for receiving a reference voltage. Forexample, the reference voltage may be a ground voltage (0 V), which maybe provided through wired lines within all the electronic circuits ofthe electronic system 100 a (as represented in the figure through linesbeing connected to the electrical symbol of the ground).

A metal plate 120 a is formed in an area 130 being outside thefunctional region 108 a of the electronic circuit 105 a, while anothermetal plate 120 a′ is formed in an area 130′ being outside thefunctional region 108 a′ of the electronic circuit 105 a′.

Such metal plates 120 a and 120 a′ are arranged in parallel being facingto each other at a suitable distance, so as to form a capacitor 123 ahaving as dielectric medium, for example, the air being interposedbetween the electronic circuits 105 a, 105 a′ (beyond any insulatingprotection layers thereof).

In the described exemplary embodiment, the area 130 of the electroniccircuit 105 a also includes an inductor 125 a; the inductor 125 a has afirst terminal being coupled to a terminal 103 a of the transceiver 110a and a second terminal being coupled with the metal plate 120 a.

The metal plate 120 a′ of the electronic circuit 105 a′, instead, isdirectly coupled with the terminals 103 a′ of the transceiver 110 a′.

In this way, the inductor 125 a and the capacitor 123 a form a seriesresonant LC circuit 125 a, 123 a; such LC circuit 125 a, 123 a has aresonance frequency (whose value depends on the size of the inductor 125a and of the capacitor 123 a) at which ideally it behaves like a shortcircuit, so that each signal at the resonance frequency may betransmitted through it (from the transceiver 110 a of the electroniccircuit 105 a to the transceiver 110 a′ of the electronic circuit 105a′, and vice-versa), ideally without any loss.

An embodiment is advantageous since it does not require that eachelectronic circuit 105 a, 105 a′ should be provided with a wholeresonant LC circuit, with considerable saving in area occupation.

In fact, the corresponding inductor may be present in only one of theelectronic circuits 105 a, 105 a′ (such as for the inductor 125 a of theelectronic circuit 105 a in the example at issue).

In any case, the capacitor 123 a is distributed on the two electroniccircuits 105 a, 105 a′; in particular, each electronic circuit 105 a,105 a′ includes one plate 120 a, 120 a′ only of such capacitor 123 a,while the respective dielectric medium is formed outside the electroniccircuit 105 a, 105 a′ (for example, through the air being interposedbetween them).

All of this may have a beneficial effect on the size of the electroniccircuits 105 a, 105 a′, and hence of the whole electronic system 100 a.

In FIG. 1B there is schematically shown an electronic system 100 bexploiting wireless signal transmission according to another embodiment.

The electronic system 100 b includes two electronic circuits 105 b and105 b′ comprising the same components described above.

In such embodiment, in the area 130 of the electronic circuit 105 bthere is formed a further metal plate 120 b, and in the area 130′ of theelectronic circuit 105 b′ there is formed a further metal plate 120 b′,which two plates form a further capacitor 123 b.

The area 130 of the electronic circuit 105 b includes a further inductor125 b; the inductor 125 b has a first terminal being coupled with thereference terminal 104 a of the transceiver 110 a and a second terminalbeing coupled with the metal plate 120 b.

The metal plate 120 b′, instead, is directly connected to the referenceterminal 104 a′ of the transceiver 110 a′ of the electronic circuit 105b′.

As above, the inductor 125 b and the capacitor 123 b form a furtherseries resonant LC circuit 125 b, 123 b.

The configuration thus obtained allows implementing a differentialtransmission of the signals between the electronic circuit 105 b (at theterminals 103 a and 104 a) and the electronic circuit 105 b′ (at theterminals 103 a′ and 104 a′).

The implementations being depicted in FIG. 1A-1B may also benefit ofmanufacturing improvements for allowing an optimal management of thearea occupation of the electronic circuits within the correspondingelectronic system; for example, the inductors 125 a, 125 b may bedistributed at least partly on several circuits.

FIG. 2A-2E schematically show electronic circuits with differentimplementations of the corresponding metal plates according tocorresponding embodiments.

With particular reference to FIG. 2A, an electronic circuit 205 aincludes a functional substrate 206 being formed on a semiconductorsubstrate 215; the functional substrate 206 includes a plurality ofactive areas (not shown in the figure) being adapted to carry outspecific functions of the electronic circuit 205 a, and metal layers(not shown in the figure) for electrically connecting such active areas.

A passivation layer 207 is formed on the functional substrate 206 forpreserving it from corrosion, contamination and actions of externalsubstances.

The passivation layer 207, however, does not completely cover a lastmetal layer; the portions of the last metal layer being not covered bythe passivation layer 207 form pads 220 a (only one shown in the figureas a dark rectangle) for coupling the functional substrate 206 of theelectronic circuit 205 a with other electronic devices (not shown in thefigure).

An embodiment provides that the pad 220 a is used directly as metalplate.

Moreover, on the metal plate 220 a there may be formed a layer ofdielectric material 222 a; in this way, it is possible to increase thevalue of the capacity of the corresponding capacitor (being obtained byapproaching the other metal plate, not shown in the figure, to the layerof dielectric material 222 a).

An embodiment is advantageous since it allows minimizing the additionaloperation being required for achieving the desired result.

Turning now to FIG. 2B, an electronic circuit 205 b has a similarstructure to that shown in FIG. 2A.

In this case, a pad 210 is used for contacting the metal plate, which isformed by a substantially rectangular layer of metallic material 220 bbeing deposited on the pad 210 and on a portion of the passivation layer207 around the pad 210.

In this embodiment as well, it is possible to form a layer of dielectricmaterial 222 b on the metal plate 220 b (obtaining the same or a similaradvantage as described above).

An embodiment is advantageous since it is possible to increase thesurface of the metal plate 220 b, and thus the capacity of thecapacitor, by using a pad 210 having reduced area.

With reference now to FIG. 2C, an electronic circuit 205 c has a similarstructure to that shown in FIG. 2B (omitting the layer of dielectricmaterial for the sake of simplicity), with the difference that a metalplate 220 c having a herringbone structure (also called interdigitated)is formed on the pad 210 and on a portion of the passivation layer 207.

An example of part of the interdigitated structure of the metal plate220 c is shown in plan view in FIG. 2C below.

The metal plate 220 c includes a longitudinal metal strip 225 c;transversal metal strips 230 c extend perpendicularly to the metal strip225 c (for example, at an equal distance at their sides); one of suchtransversal metal strips having a greater width (being differentiatedthrough the reference 230 c′) contacts the pad 210.

An embodiment is advantageous since it allows using the metal plate 220c as a further means for wireless signal transmission; in fact, inparticular conditions of charge migration within the metal plate 220 c,this behaves as a set of Hertzian dipole antennas.

With reference now to FIG. 2D, an electronic circuit 205 d again has asimilar structure to that shown in FIG. 2B (omitting the layer ofdielectric material for the sake of simplicity), with the differencethat after having deposited the passivation layer 207, this is processedso as to remove it selectively (for example, through an etching process)in order to form a series of holes 240 d (that leave exposed portions ofan oxide layer, not shown in the figure, being placed on a surface areaof the functional substrate 206).

Then, a metal plate 220 d is formed on the pad 210, on a portion of thepassivation layer 207 d around the pad 210 (including the holes 240 d)and on the portions of the oxide layer being exposed in such holes 240d, so as to obtain a non-planar structure (with depressions incorrespondence to the holes 240 d, which may also extend partly withinthe functional substrate 206).

An embodiment is advantageous since the shaped profile of the metalplate 220 d allows implementing capacitors with capacity of higher valuewith respect to the previous embodiments, since this increases the areaof the metal plate 220 d but maintaining limited its encumbrance (andthus the size of the whole electronic circuit) in terms of occupiedsurface area.

Turning now to FIG. 2E, an electronic circuit 205 e again has a similarstructure to that shown in FIG. 2B, with the difference that the layerof dielectric material being formed on the metal plate 220 b (indicatedby the reference 222 e) is now provided with metal particles 250 e (onlyfour shown in the figure), each one including positive charges (blackregion) and negative charges (white region).

When a voltage is applied to the metal plate 220 b (by the signal to betransmitted), the layer of dielectric material 222 e is subject to acorresponding electric field. By electric induction, such electric fieldrotates the positive and the negative charges of each metal particle 250e along the direction of the electric field; this creates a pseudo-metalplate in addition to the metal plate 220 b (which thus may also beomitted, with the layer of dielectric material 222 e being in directcontact with the pad 210). Moreover, with high densities of theparticles 250 e, metal “bridges” (between the metal plates) within thelayer of dielectric material 222 e may possibly be formed.

An embodiment is advantageous since the properties of signaltransmission may be improved by the metal bridges; in particular, insuch way it may also be possible to transmit direct signals, such as asupply voltage of the electronic system. Moreover, the presence of theparticles 250 e may allow compensating a possible misalignment betweenthe metal plate 220 b and the other metal plate (not shown in thefigure) being placed on the layer of dielectric material 222 e.

FIG. 2F schematically shows two electronic circuits (indicated by thereferences 205 f, 205 f′) in cross-section with an implementation of themetal plates according to another embodiment. The electronic circuit 205f again has a similar structure to that shown in FIG. 2B, with thedifference that the metal plate and the corresponding layer ofdielectric material (indicated by the references 220 f and 222 f,respectively) have a shape that is complementary to a shape of the othermetal plate and the corresponding layer of dielectric material of theelectronic circuit 205 f′ (indicated with the references 220 f′ and 222f′, respectively

In the example in FIG. 2F, the metal plate 220 f and the layer ofdielectric material 222 f of the electronic circuit 205 f have a convextrapezoidal shape; such shape may be obtained from the structure beingdepicted in FIG. 2B by smoothing out the metal plate 220 b through aknown technique of chemical etching or by forming a bump according toany known technique. The concave trapezoidal structure is obtained byfirstly forming a groove in a functional substrate 206′ (which is madeon a semiconductor substrate 215′ and it is covered by a passivationlayer 207′), then forming a metal plate 220 f′ within the same groove,and finally depositing the layer of dielectric material 222 f′ onto themetal plate 220 f′.

It is noted that the concave shape of the metal plate 220 f′ and of thelayer of dielectric material 222 f′ is formed within the functionalsubstrate 206′; in this way, a reduction of the encumbrance of theelectronic circuit 205 f′ is obtained at the expense of a reduction inthe working volume of its functional substrate 206′, wherein theconnections between the active and/or passive components may be made. Inan alternative embodiment (not shown in the figure), the concavetrapezoidal shape may be formed outside the functional substrate throughdeposition of a metal layer and subsequent etching thereof with thefinal deposition of the layer of dielectric material. In this secondcase, it is obtained a greater encumbrance of the electronic circuitwithout affecting the working volume of its functional substrate.

An embodiment is advantageous since, by exploiting mechanicallyself-centering metal plates, it allows avoiding misalignments betweensuch metal plates that might cause undesired changes of the capacity andhence of the resonance frequency of the resonant LC circuit.

The embodiments being described from FIG. 2A to FIG. 2F do not cover allthe possible implementations, because they are only exemplary and notlimitative embodiments. Moreover, is understood that such embodimentsmay be combined with each other, providing further implementations thathowever fall within the scope of the present disclosure.

Referring now to FIG. 3A, there are schematically shown differentimplementations of the metal plate and of the inductor of the resonantLC circuit in top view according to corresponding embodiments. Theelectronic circuits have a structure being substantially equivalent tothat shown in FIG. 2B, with the difference that both the metal plate andthe inductor (not visible in the figure) are formed on the passivationlayer. What differentiates the three embodiments represented in FIG. 3Ais the mutual arrangement of the metal plate and of the inductor (beingformed by a winding having a proper number of coils). In a firstembodiment of the electronic circuit being indicated with the reference305 a ₁, a metal plate 320 a ₁ and an inductor 325 a ₁ are put side byside. In a second embodiment of the electronic circuit being indicatedwith the reference 305 a ₂, a metal plate 320 a ₂ is around an inductor325 a ₂ (that is, outside its winding). In a third embodiment of theelectronic circuit being indicated with the reference 305 a ₃, a metalplate 320 a ₃ is both around an inductor 325 a ₃ and within it; inaddition, the metal plate 320 a ₃ is shaped like a coil of the inductor325 a ₃. In any case, such shaping may also be used for the metal plate320 a ₂ of the second embodiment.

The embodiment of the electronic circuit 305 a ₁ may be usefullyimplemented by using standard production processes; therefore, suchembodiment may be used for making electronic devices having reducedcosts.

The embodiments of the electronic devices 305 a ₂ and 305 a ₃ may beusefully exploited for avoiding unwanted coupling between neighboringelectronic circuits; in fact, the metal plate 320 a ₂, 320 a ₃ aroundthe inductor 325 a ₂, 325 a ₃ may cause an effect of segregation of itsmagnetic field.

In addition, the embodiment of the electronic circuit 305 a ₃ takes fulladvantage of the available area, so as to obtain capacitors with highercapacity for the same area occupation, or to reduce the area occupationfor the same capacity (thanks to the portion of the metal plate 320 a ₃within the inductor 325 a ₃.

Turning to FIG. 3B, there is schematically shown an embodiment of theelectronic circuit in cross-section (indicated by the reference 305 b)with an implementation of the metal plate and of the inductor (indicatedwith the references 320 b and 325 b, respectively) according to anotherembodiment. The electronic circuit 305 b, having substantially the samestructure as that shown in FIG. 2B, has the metal plate 320 b beingformed on a passivation layer 307; such metal plate 320 b is connectedto a pad 310 being connected to an inductor 325 b, which is formedwithin the functional substrate 306 being located above thesemiconductor substrate 315.

In such an embodiment the inductor 325 b may affect the size of theelectronic circuit 305 b, but this may be reduced by increasing thevalue of the inductance of the inductor 325 b by using, for example,magnetic vias 330 b within a winding forming the inductor 325 b.

FIG. 4A schematically shows an electronic system 400 a according toanother embodiment. The electronic system 400 a includes theabove-described electronic circuit 105 a (see FIG. 1A) and anotherelectronic circuit 405 a having substantially the same structure (whosecomponents are indicated with the same references but replacing thefirst digit 1 with the digit 4).

In the electronic system 400 a the metal plates 120 a and 420 a of theelectronic circuits 105 a and 405 a, respectively, are arranged inparallel facing each other, as well as the respective inductors 125 aand 425 a. In this way, the signal transmission between the twoelectronic circuits 105 a and 405 a may occur through the resonantchannel being created by the virtual short circuit that is createdbetween the two metal plates 120 a and 420 a and, at the same time,through the magnetic coupling that, by electromagnetic induction, existsbetween the inductors 125 a and 425 a.

An embodiment of exploiting both a capacitive transmission and aninductive transmission may be advantageous since the signal detected bythe transceivers 110 a, 410 a turns out to have an amplitude beinggreater with respect to the case of the capacitive transmission only;this may lead to a good signal to noise ratio in the phase ofacquisition and subsequent processing of the signals.

FIG. 4B schematically shows an electronic system 400 b according to afurther embodiment. The electronic system 400 b includes theabove-described electronic circuits 105 a and 105 a′ and a furtherelectronic circuit 405 b. The electronic circuit 405 b includes, asabove, a functional region 408 b, a transceiver 410 b, and terminals 403b, 404 b, with the difference that in an area 430 outside the functionalregion 408 b there is formed an inductor 425 b (instead of a metalplate) being coupled between the terminals 403 b and 404 b of thetransceiver 410 b.

With an embodiment, the electronic circuit 105 a may transmit signalssimultaneously to the electronic circuit 105 a′ (by capacitivetransmission through the resonant channel between the respective metalplates 120 a and 120 a′) and to the electronic circuit 405 b (byinductive transmission because of electromagnetic induction between therespective inductors 125 a and 425 b), and vice-versa.

Such embodiment may be particularly advantageous since it allows thesimultaneous transmission of signals among multiple circuits of the sameelectronic system in different modes. Moreover, further advantages maybe obtained by implementing the embodiments being shown in FIG. 4A andFIG. 4B in differential configuration as described for FIG. 1B.

With reference to FIG. 5A, there is schematically shown animplementation of the electronic system 400 a according to anembodiment. In such case, the electronic circuits (indicated with thereferences 505 a and 505 a′) have different sizes. Each electroniccircuit 505 a, 505 a′ includes a semiconductor substrate 515 a, 515 a′on which a functional substrate 506 a, 506 a′ is placed; on thefunctional substrate 506 a, 506 a′ there is deposited a passivationlayer 507 a, 507 a′ in which a pad 510, 510′ is formed. On thepassivation layer 507 a, 507 a′ of each electronic circuit 505 a, 505 a′there are formed a metal plate 520 a, 520 a′ and an inductor 525 a, 525a′ around it. The electronic circuits 505 a, 505 a′ are placed inface-to-face configuration, in which the metal plate 520 a and theinductor 525 a of the electronic circuit 505 a are arranged frontallyand parallel to the metal plate 520 a′ and to the inductor 525 a′ of theelectronic circuit 505 a′, respectively.

The area included between the passivation layers 507 a and 507 a′ of theelectronic circuits 505 a and 505 a′ may be filled with dielectricmaterial 522 a for increasing the capacitive coupling. The pads 510 a ofthe electronic circuit 510 a and the pads 510 a′ of the electroniccircuit 505 a′ may be connected to external circuits or to each other byusing wires (wire bonds in jargon) or contact bumps.

It may also be possible to have the electronic circuit 505 a and theelectronic circuit 505 a′ in a configuration known as face-to-back (notshown in the figure), which differs from the face-to-face configurationbecause in one of the two electronic circuits the capacitive plate andthe inductor are made under the semiconductor substrate. In this case itmay be necessary to use at least one metal via (in jargon, ThroughSilicon Via, or TSV) for connecting the capacitive plate and theinductor to the functional substrate by passing through thesemiconductor substrate.

Also other configurations not shown in any figure may be implemented,such as, for example, the back-to-back and back-to-face configurations,even in the differential configuration; moreover, the metal plate may bepresent above the passivation layer and the inductor may be presentunder the semiconductor substrate (or vice-versa), and they may beconnected to each other through TSVs. Possibly, one of the surfaces ofthe TSV itself may be used as a capacitor plate.

Referring now to FIG. 5B, there is schematically shown an implementationof the electronic system 400 a according to another embodiment. In suchcase, two electronic circuits 505 b, 505 b′ are implemented in insulatedareas of a common functional substrate 506 b, being arranged on asemiconductor substrate 515 b and being covered by a passivation layer507 b. Each electronic circuit 505 b, 505 b′ includes a metal plate 520b, 520 b′ and an inductor 525 b, 525 b′ that are made within thefunctional substrate 506 b. Naturally, even in this case by implementinga differential configuration the electronic circuits 505 b, 505 b′ maybe separated galvanically from each other but may remain capable ofcommunicating with each other.

An embodiment may be advantageous since it does not require the assemblyof two different electronic circuits and it does not require any furtherlayer of dielectric material; in fact, it may be possible to use atleast one oxide layer being already present in the functional substrate506 b, which acts as insulator between the metal plates 520 b, 520 b′and the inductors 525 b and 525 b′.

These and other implementations (even hybrid ones), possibly with propermodifications, may be applied to make other electronic systems thatexploit the wireless signal transmission, such as, for example, theelectronic system of FIG. 4B.

Naturally, in order to satisfy local and specific requirements, one mayapply to the embodiments described above many logical and/or physicalmodifications and alterations. More specifically, although embodimentshave been described with a certain degree of particularity, it isunderstood that various omissions, substitutions and changes in the formand details as well as other embodiments are possible. In particular,the same embodiments may even be practiced without the specific detailsset forth in the preceding description for providing a more thoroughunderstanding thereof; on the contrary, well known features may havebeen omitted or simplified in order not to obscure the description withunnecessary particulars. Moreover, it is expressly intended thatspecific elements and/or method steps described in connection with anydisclosed embodiment may be incorporated in any other embodiment as amatter of general design choice.

For example, similar considerations apply if the electronic circuitshave a different structure or include equivalent components (eitherseparated from each other or combined together, in whole or in part); inparticular, it may be possible to provide that the electronic circuitsare included in different packages.

Similar considerations may apply if the second metal plate is formed bydistinct metal plates, each one being coupled with different electroniccircuits or different functional blocks of a same electronic circuit.

Nothing prevents coupling the first metal plate with different inductors(for example, being connected to each other through series, parallel, T,or Y connections, and/or through any other useful possible combinationthereof) for creating multiple resonant channels with differentelectronic circuits and/or with different functional blocks of a sameelectronic circuit. In this case, each resonant channel will turn out tobe active in correspondence to a signal having the specific resonancefrequency for the given channel.

The same considerations may apply if at least partly variable inductorsand/or capacitors are used for properly modifying the resonancefrequencies, for example, for compensating any fluctuations in theresonant frequencies being due to parasitic effects or productionimperfections. Proper circuits, some of which may be, for example,gyrators (possibly similar to the Antoniou circuit), may be used foremulating a variable inductance, such as being capable of maximizing thesystem performance according to at least one electrical parameter beingmeasured by such circuits. Instead of changing the inductance, suitablecircuits (for example, a programmable frequency oscillator) may be usedfor varying the frequency according to the resonant circuit and theimperfections thereof, thereby allowing maximizing the transmitted powerthrough proper adaptive algorithms being applied by control circuitsthat measure at least one parameter of the transmitted and receivedsignal. At high-frequency the generic inductor may be replaced by aproper transmission line whose effect and functionality are, however,equivalent thereto.

Nothing prevents forming the first metal plate by a plurality of metalplates, each one being coupled, through a corresponding plurality ofinductors, with a corresponding plurality of electronic circuits orfunctional blocks of a same electronic circuit.

Similar considerations may apply if the metal plates have shapes beingoptimized as a function of their area occupation, such as, for example,rhomboidal ones, or if the metal plates are not plane and parallel, but,for example, coaxial cylindrical or concentric spherical ones.

Moreover, nothing prevents making the first capacitive plate insideand/or outside the coils of the inductor of a metal that, at theresonance frequency, has ferromagnetic properties (for example, magneticpermeability greater than 10), such as, for example, nickel and itsalloys or cobalt and its alloys, in order to increase the inductance ofthe inductor.

Nothing prevents making the resonant LC circuit (or part thereof) withinthe passivation layer or below it; moreover, nothing prevents making theresonant LC circuit (or part thereof) within an oxide layer or ofanother material.

The same considerations may apply if the dielectric layer between thefirst metal plate and the second metal plate is not present, forexample, by exploiting a fluid (for example, the air) being interposedbetween the two plates as dielectric

The same considerations may apply if the conductive particles are notwithin the layer of dielectric material but in the passivation layer(for example, in case that, in order to reduce the area occupation,there becomes necessary to remove the layer of dielectric material andto use the existing passivation layer as dielectric).

Moreover, the same considerations may apply if the first capacitiveplate and the second capacitive plate have a more complex profile, suchas sawtooth-like.

Nothing prevents having the capacitive plates not around the respectiveinductors, but, for example, only within them.

Similar considerations may apply if the electronic circuits are providedwith further metal plates to be used, for example, in dummy mode forobtaining a mechanical self-alignment of the first and second metalplates.

Furthermore, in all the described embodiments wherein it is desired toperform the simultaneous transmission of signals among multiple circuitsin different modes (i.e., capacitively and inductively), such atransmission may be implemented in different ways according tocorresponding specific requirements. For example, alternatively to thepossibility (previously described) of using the signal at approximatelythe resonant frequency to be transmitted both capacitively andinductively, the signal may spread over a frequency range around theresonant frequency; in this way, each frequency of the range may beproperly used for a corresponding transmission, as a sort of “dedicatedcommunication channel”. Additionally or alternatively, it may also bepossible to provide the use of different signals to be transmitted in analternated way with respect to each other, for example, by using asignal for a capacitive transmission with a corresponding circuitfollowed by another signal for an inductive transmission to anothercorresponding circuit (or vice versa). Also for the latter case, thefrequencies of the alternated signals may be approximately equal to eachother (and approximately equal to the resonant frequency) or differentto each other (but however within a proper frequency range around theresonant frequency for avoiding any excessive loss of intensity of thetransmitted signal).

The proposed embodiments might be part of the design of an integratedcircuit. The design may also be created in a programming language;moreover, if the designer does not fabricate chips or masks, the designmay be transmitted by physical means to others. In any case, theresulting integrated circuit may be distributed by its manufacturer inraw wafer form, as a bare die, or in packages. Moreover, the proposedembodiments may be integrated with other circuits in the same chip, orit may be implemented in intermediate products, such as PCBs (PrintedCircuit Boards) or on a generic substrate (for example, of the ceramictype), and coupled with one or more other chips (such as a processor ora memory). In any case, the integrated circuit may be suitable to beused in complex systems (such as computers).

In addition, the metal plate and/or the inductor may also be madeoutside the integrated circuit—for example, on a PCB or on a genericsubstrate (for example, of the ceramic type), together with the possibledielectric layer either including or not metal particles. For example,this may be useful for creating interfaces for the test of the describedelectronic circuits.

The proposed structure may be part of the design of an integratedsystem. The design may also be created in a programming language;moreover, if the designer does not manufacture the electronic system orthe masks, the design may be transmitted by physical means to others. Inany case, the resulting integrated system may be distributed by itsmanufacturer in raw wafer form, as a bare die, or in packages. Moreover,the proposed structure may be integrated with other circuits and in thesame chip, or it may be mounted in intermediate products (such as motherboards) and coupled with one or more other chips (such as a processor).In any case, the integrated system may be suitable to be used in complexsystems (such as automotive applications or microcontrollers).

Moreover, embodiments of the described electronic circuits may beimplemented and sold separately.

Furthermore, an embodiment may lend itself to be implemented through anequivalent method (by using similar steps, removing some steps being notessential, or adding further optional steps); moreover, the steps may beperformed in a different order than discussed above, concurrently, or inan interleaved way (at least partly).

From the foregoing it will be appreciated that, although specificembodiments have been described herein for purposes of illustration,various modifications may be made without deviating from the spirit andscope of the disclosure. Furthermore, where an alternative is disclosedfor a particular embodiment, this alternative may also apply to otherembodiments even if not specifically stated.

The invention claimed is:
 1. An electronic system, comprising: a firstelectronic circuit; a second electronic circuit; a resonant LC circuithaving a resonance frequency for coupling the first electronic circuitand the second electronic circuit, each electronic circuit configured toprovide a signal at the resonance frequency to be transmitted to theother electronic circuit through the LC circuit; wherein the LC circuitincludes an interdigitated capacitor having at least one first capacitorplate included in the first electronic circuit and at least one secondcapacitor plate included in the second electronic circuit, a firstinductor included in the first electronic circuit, the at least onecapacitor plate of the first electronic circuit being coupled with oneof the electronic circuits through the inductor.
 2. The electronicsystem according to claim 1, wherein the first electronic circuit isintegrated in a first chip and the second electronic circuit isintegrated in a second chip distinct from the first chip, and whereinthe inductor and the capacitor of each electronic circuit are integratedin the corresponding chip.
 3. The electronic system according to claim1, wherein the first electronic circuit and the second electroniccircuit are integrated in a first region and a second region,respectively, of a common chip, the first region being insulated fromthe second region.
 4. The electronic system according to claim 1,further including at least one dielectric layer arranged between the atleast one first capacitor plate and the at least one second capacitorplate.
 5. The electronic system according to claim 1, wherein the atleast one dielectric layer embeds conductive particles.
 6. Theelectronic system according to claim 1, wherein at least one capacitorplate includes a conductive longitudinal strip, and a plurality ofconductive transversal strips extending from the longitudinal strip. 7.The electronic system according to claim 1, wherein at least onecapacitor plate has a non-planar structure with a plurality ofdepressions.
 8. The electronic system according to claim 1, wherein atleast one capacitor plate extends around the corresponding inductormeans in a plan view.
 9. The electronic system according to claim 1,wherein each electronic circuit includes an inductor and is furtherconfigured to provide a further signal at a further frequency to betransmitted to the other electronic circuit and/or for receiving thefurther signal from the other electronic circuit, the further frequencybeing equal to or different from the resonance frequency.
 10. Theelectronic system according to claim 1, wherein at least one firstcapacitor plate has a convex profile matching a concave profile of acorresponding second capacitor plate.
 11. A method for transmittingsignals in an electronic system from a first electronic circuit to asecond electronic circuit, wherein the method includes the steps of:coupling the first electronic circuit and the second electronic circuitthrough a resonant LC circuit having a resonance frequency, transmittinga signal at the resonance frequency from the first electronic circuit tothe second electronic circuit through the LC circuit, and wherein thestep of coupling the first electronic circuit and the second electroniccircuit through a resonant LC circuit includes: coupling at least onefirst capacitor plate included in the first electronic circuit and atleast one second capacitor plate included in the second electroniccircuit to form a capacitor, a portion of the capacitor with a firstinductor included in the first electronic circuit and disposed withinturns of an inductor winding.
 12. An electronic system, comprising: afirst electronic circuit; a second electronic circuit; a resonant LCcircuit having a resonance frequency for coupling the first electroniccircuit and the second electronic circuit, each electronic circuitconfigured for receiving a signal at the resonance frequency from theother electronic circuit through the LC circuit, wherein the LC circuitincludes an interdigitated capacitor having at least one first capacitorplate included in the first electronic circuit and at least one secondcapacitor plate included in the second electronic circuit, and a firstinductor included in the first electronic circuit, the at least onecapacitor plate of the first electronic circuit being coupled with thefirst electronic circuit through the inductor.
 13. An apparatus,comprising: a first electronic circuit having a first signal node; and afirst conductive electrode coupled to the first signal node andconfigured to form a first capacitor with a second conductive electrodethat is coupled to a second signal node of a second electronic circuitsuch that a first signal may propagate between the first and secondsignal nodes via the capacitor; further comprising: an inductor seriallycoupled between the first signal node and the first conductiveelectrode; wherein the inductor includes a winding having turns; andwherein the first conductive electrode includes a portion disposedbetween the turns of the winding.
 14. An apparatus, comprising: a firstelectronic circuit having a first signal node; and a first conductiveelectrode coupled to the first signal node and configured to form afirst capacitor with a second conductive electrode that is coupled to asecond signal node of a second electronic circuit such that a firstsignal may propagate between the first and second signal nodes via thecapacitor; further comprising: a ferromagnetic material; and an inductorserially coupled between the first signal node and the first conductiveelectrode and having a portion disposed around the ferromagneticmaterial.
 15. An apparatus, comprising: a first electronic circuithaving a first signal node; and a first nonplanar conductive electrodecoupled to the first signal node and configured to form a firstcapacitor with a second conductive electrode that is coupled to a secondsignal node of a second electronic circuit such that a first signal maypropagate between the first and second signal nodes via the capacitor;wherein the first conductive electrode comprises an interdigitatedelectrode.
 16. The apparatus of claim 15, further comprising an inductorserially coupled between the first signal node and the first conductiveelectrode.
 17. The apparatus of claim 15, further comprising: whereinthe first electronic circuit has a third signal node; and a thirdconductive electrode coupled to the third signal node and configured toform a second capacitor with a fourth conductive electrode that iscoupled to a fourth signal node of the second electronic circuit suchthat a second signal may propagate between the third and fourth signalnodes via the second capacitor.
 18. The apparatus of claim 17, furthercomprising an inductor serially coupled between the third signal nodeand the third conductive electrode.
 19. The apparatus of claim 15,further comprising: an inductor serially coupled between the firstsignal node and the first conductive electrode and disposed around aportion of the first conductive electrode.
 20. The apparatus of claim15, further comprising: a semiconductor die; and wherein the firstelectronic circuit and the first conductive electrode are disposed onthe die.
 21. The apparatus of claim 15 wherein the first conductiveelectrode is disposed within at least one trench.
 22. The apparatus ofclaim 15, further comprising a dielectric disposed adjacent to the firstconductive electrode.
 23. The apparatus of claim 15, further comprisinga dielectric disposed adjacent to the first conductive electrode, thedielectric including at least one electrically conductive particle. 24.The apparatus of claim 15, further comprising: a substrate; and whereinthe first conductive electrode protrudes from the substrate.
 25. Theapparatus of claim 15, further comprising: an inductor serially coupledbetween the first signal node and the first conductive electrode;wherein the inductor includes a winding; and wherein the firstconductive electrode is disposed over the winding.
 26. The apparatus ofclaim 15, further comprising: an inductor serially coupled between thefirst signal node and the first conductive electrode; wherein theinductor includes a winding; and wherein the first conductive electrodeis disposed adjacent to the winding.
 27. The apparatus of claim 15,further comprising: a substrate; and wherein the first electroniccircuit and the first conductive electrode are disposed on thesubstrate.
 28. The apparatus of claim 15, further comprising: aninductor serially coupled between the first signal node and the firstconductive electrode; and wherein the first conductive electrodeincludes a portion that is disposed around the inductor.
 29. A system,comprising: a first apparatus including a first electronic circuithaving a first signal node; a first conductive electrode in the firstelectronic circuit and electrically coupled to the first signal node;and a first inductor serially coupled between the first signal node andthe first conductive electrode and having a portion disposed around aferromagnetic material; and a second apparatus including a secondelectronic circuit having a second signal node; and a second conductiveelectrode electronically coupled to the second signal node and forming afirst capacitor with the first conductive electrode.
 30. The system ofclaim 29 wherein the second apparatus further includes a second inductorserially coupled between the second signal node and the secondconductive electrode.
 31. The system of claim 29 wherein the secondapparatus further includes a second inductor serially coupled betweenthe second signal node and the second conductive electrode andmagnetically coupled to the first inductor.
 32. The system of claim 29wherein: the second electronic circuit further includes a third signalnode; and the second apparatus further includes a second inductorelectrically coupled to the third signal node and magnetically coupledto the first inductor.
 33. The system of claim 29 wherein the first andsecond apparatuses are disposed on a same integrated-circuit die. 34.The system of claim 29 wherein the first and second apparatuses aredisposed on respective integrated-circuit dies.
 35. The system of claim29 wherein the first and second apparatuses are disposed on a samesubstrate.
 36. The system of claim 35 wherein the substrate comprises asemiconductor substrate.
 37. The system of claim 35 wherein thesubstrate comprises a printed circuit board.
 38. The system of claim 29wherein the first and second apparatuses are disposed on respectivesubstrates.
 39. The system of claim 29 wherein: the first apparatusfurther includes the first electronic circuit having a third signalnode; a third conductive electrode electrically coupled to the thirdsignal node; and the second apparatus further includes the secondelectronic circuit having a fourth signal node; and a fourth conductiveelectrode electronically coupled to the fourth signal node and forming asecond capacitor with the third conductive electrode.
 40. The system ofclaim 39 wherein the first apparatus further includes a second inductorserially coupled between the third signal node and the third conductiveelectrode.
 41. The system of claim 39 wherein the second apparatusfurther includes a second inductor serially coupled between the fourthsignal node and the fourth conductive electrode.
 42. A method,comprising: conducting a first signal having a first frequency with afirst inductor and a first conductive electrode wherein the firstelectrode includes a winding having turns such that the first conductiveelectrode is disposed in the turns; capacitively coupling the signalbetween the first conductive electrode in a first electronic circuit anda second conductive electrode that forms a capacitor with the firstconductive electrode, a resonant frequency corresponding to acombination of the inductor and the capacitor being approximately equalto the frequency of the signal.
 43. The method of claim 42, furthercomprising: generating the signal with a first circuit that is disposedon first platform with, and that is electrically coupled to, theinductor and first conductive electrode; and receiving the signal with asecond circuit that is disposed on a second platform with, and that iselectrically coupled to, the second conductive electrode.
 44. The methodof claim 42, further comprising: generating the signal with a firstcircuit that is disposed on a first platform with, and that iselectrically coupled to, the second conductive electrode; and receivingthe signal with a second circuit that is disposed on a second platformwith, and that is electrically coupled to, the inductor and firstconductive electrode.
 45. The method of claim 42 wherein conducting thesignal comprises conducting the signal with a series combination of theinductor and the first conductive electrode.
 46. The method of claim 42,further comprising magnetically coupling the signal from the firstinductor to a second inductor that is electrically coupled to the secondconductive electrode, the resonant frequency corresponding to acombination of the first and second inductors and the capacitor beingapproximately equal to the frequency of the signal.
 47. The method ofclaim 42, further comprising magnetically coupling the signal from thefirst inductor to a second inductor that is electrically uncoupled fromthe second conductive electrode.
 48. The method of claim 42, furthercomprising: conducting a second signal having a second frequency with asecond inductor and a third conductive electrode; and capacitivelycoupling the second signal between the third conductive electrode and afourth conductive electrode that forms a second capacitor with the thirdconductive electrode, a second resonant frequency corresponding to acombination of the second inductor and the second capacitor beingapproximately equal to the second frequency of the second signal.
 49. Anapparatus, comprising: a first electronic circuit having a first signalnode; an inductor having a winding with turns and a first node coupledto the signal node and having a second node; and a first conductiveelectrode disposed in the turns of the winding and coupled to the secondnode of the inductor and configured to form a first capacitor with asecond conductive electrode that is coupled to a second signal node of asecond electronic circuit such that a first signal may propagate betweenthe first and second signal nodes via the inductor and capacitor.
 50. Anapparatus, comprising: a first electronic circuit having first andsecond signal nodes; a first interdigitated conductive electrode coupledto the first signal node and configured to form a first interdigitatedcapacitor with a second interdigitated conductive electrode that iscoupled to a third signal node of a second electronic circuit such thata first signal may propagate between the first and third signal nodesvia the first capacitor; an inductor having a first node coupled to thesecond signal node and having a second node; and a third conductiveelectrode coupled to the second node of the inductor and configured toform a second capacitor with a fourth conductive electrode that iscoupled to a fourth signal node of the second electronic circuit suchthat a second signal may propagate between the third and fourth signalnodes via the inductor and the second capacitor.